VW / Audi / Seat / Skoda (VAG) Siemens Simos 9.1 Engine ECU Repairs

Type: Siemens
Fits: VAG – Audi / Seat / Skoda / Volkswagen (VW)
Fuel: Petrol
Ref: ECUT218195

Note: This ECU may also fit other models.

BBM, BMD, BZG and BME are the four engine codes that matter on this page. In the records behind it, each one is attached to a single Siemens Simos 9.1 reference from the table at the foot of the page, which makes the code a sharper guide to the unit than the car it came out of. We repair all four of these engine ECUs, and what follows sets out which code goes with which.

Why the car alone will not identify a Simos 9.1

Every unit on this page is a 1.2 petrol ECU made by Siemens, and many are labelled Siemens VDO. The same three small cars recur against them: the Volkswagen Polo, the Skoda Fabia and the Seat Ibiza.

The Polo and the Fabia are recorded against all four references. The Ibiza is recorded against the two that begin 03E. A 1.2 Polo or Fabia with a suspect ECU could therefore be carrying any of the four, and naming the car does not narrow it.

The engine code does, and the next section shows how.

Which Simos 9.1 goes with BBM, BMD, BZG and BME

03D 906 023, with no letter after it, is recorded in the 1.2 Polo and the 1.2 Fabia with the BBM engine.

03D 906 023 B is recorded in the same two cars with the BMD engine, which the records describe as a 6-valve unit. The same reference is also recorded in the Volkswagen Fox.

03E 906 023 B carries the BZG code against the 1.2 Polo, and is recorded in the 1.2 Fabia and the 1.2 Ibiza as well.

03E 906 023 D is the BME unit, recorded in all three cars: the Polo, the Fabia and the Ibiza, each a 1.2.

Read in reverse, BBM leads to 03D 906 023, BMD to 03D 906 023 B, BZG to 03E 906 023 B and BME to 03E 906 023 D. That is a check to hold against the label on the unit, not a statement that one of these ECUs will run a car it did not come from. Three cars sharing a reference is a record of where it has been found, nothing more.

Reading 03D and 03E on the label

The four references sit on two bases, 03D 906 023 and 03E 906 023, and the letter after the base, or the lack of one, completes the identification. The base alone is not enough: 03D covers both the BBM and the BMD units, and 03E covers both BZG and BME.

The trailing letter is a single character, easy to miss on a worn or scuffed label, and on this page it separates two different engines. Quote the whole reference, base and letter together, with the engine code alongside it if you have it.

If the label shows neither 03D 906 023 nor 03E 906 023, the unit is not one of the four covered here. Volkswagen owners can look through Polos and Foxes whose label reads otherwise, Skoda owners through the Skoda labels we cover elsewhere, and Seat owners through Ibiza fitments outside Simos 9.1. For any other make, start from the engine management systems we repair.

What happens when a Simos 9.1 reaches our workshop

Every Siemens Simos 9.1 we take in for repair is handled by our own engineers in our UK workshop. The unit is logged, inspected and electrically tested, then taken through diagnostics aimed at the fault it arrived with.

Repairs are made at component level under a microscope, using temperature-controlled rework equipment, so the fault is fixed on the original board rather than the unit being swapped. It is not signed off until it passes final testing.

Once testing is complete, we contact you with what we found and a quote. Nothing chargeable starts until you authorise it, and the repair carries a 24-month warranty.

We work by post, so the unit can come from anywhere in the UK. Have the full label reference and the engine code to hand, then put both into a quote request.

All four references are listed below.

Common part numbers associated with this type of unit